There are known headrest for seat back of cars, coaches, trains, planes, naval means or vehicles in general, fit also to the head and neck protection of the transported people.
The known headrests are often height and tilting adjustable in order to be fit for the different people builds and requirements.
Generally the known headrests are placed, or adjusted, at a certain distance from the head and for this reason they have the drawback of not providing a sufficient protection from the damages caused by the fast retrograde motion of the trunk and the head, known as whiplash, following from a collision or an accident.
There are also known vehicle seats provided with backs having mechanisms connected to the headrests in order to cause the forward motion thereof thanks to the force exerted by the people back onto the seat back.
Said headrests activated by the force impressed by the users to the seat backs, have the drawback of being extremely complex, expensive, and hard to restore in the correct working condition after the activation.
There are known headrest, actually in testing step, provided with, or associated to cushions, known as air-bag, inflated by pyrotechnic devices activated by electronic controls connected to sensors for the sensing of the accelerations following from collisions.
Said under testing known air-bags have, in addiction to the drawbacks of being complex, expensive, low-reliable in hard environmental conditions, having electronically activated pyrotechnic devices hard to restore, the drawback to be very difficult of being set and calibrated for proper activation time and conditions.